Hail, holy Queen, Mother of Mercy!
Our life, our sweetness, and our hope!
To thee do we cry, poor banished children of Eve,
to thee do we send up our sighs,
mourning and weeping in this valley, of tears.
Turn, then, most gracious advocate,
thine eyes of mercy toward us;
and after this our exile show unto us the
blessed fruit of thy womb Jesus;
O clement, O loving, O sweet virgin Mary.

V. Pray for us, O holy Mother of God
R. That we may be made worthy of the promises of Christ.

This Marian hymn is sung after Compline for most of the Liturgical year. When it is not sung, another Marian hymn more in tune with the season is sung instead. The Church prizes devotion to the Blessed Virgin Mary so highly, and deems it so necessary, that she requires it of all her priests and religious.

This hymn is actually a very common prayer: the Hail Holy Queen, recited at the end of the holy Rosary. This is in the top 5 Catholic prayers as far as general familiarity and frequency of use are concerned.

There are two chant versions of this prayer: the solemn version, sung on Sundays and feast days, and the simple version. The solemn version is longer, but they are both beautiful.